1. Field of the Invention
The present invention relates to a check valve for a refueling pipe mainly applied to a refueling pipe for a fuel tank of a vehicle.
2. Description of the Related Art
Conventionally, there has been known such a technique that a fuel tank is provided with a float valve positioned at the inlet portion of a vent path continuing to a canister so that, when fuel is fully filled within the fuel tank, the float valve is closed to stop the air breather within the fuel tank. When the float valve is closed to stop the air breather within the fuel tank in this manner, the fuel supplied from a refueling nozzle rises within the refueling pipe. Then, when the fuel thus rising within the refueling pipe reaches the tip end of the refueling nozzle, the automatic-stop mechanism of the refueling nozzle G operates to automatically stop the fuel supply.
In this case, there may arise such a so-called spitting phenomenon that, immediately after the closing of the float valve, the pressure within the fuel tank increases pulsatively due to the inertia of the fuel supplied from the refueling pipe, and so the fuel flows backward from the fuel tank side to the refueling pipe due to the reaction and rises within the refueling pipe and then spouts out of the refueling pipe before the automatic-stop mechanism of the refueling nozzle is operated.
In order to prevent such a spitting phenomenon, there has been known such a technique as disclosed in Japanese Utility Model Unexamined Laid-Open (Kokai) No. Sho. 63-88529 that a check valve for preventing the backward flow of the fuel from the fuel tank side to the refueling pipe side is provided at the end portion on the fuel tank side of the refueling pipe. This check valve is provided with a valve element which is biased by a spring toward a valve seat portion of a tapered-shape formed at the refueling pipe side of a valve casing. The valve element is pushed and opened due to the dynamic pressure of the fuel at the time of fuel supply while, when the fuel flows backward from the fuel tank side, the valve element is seated on the valve seat portion thereby to prevent the backward flow of the fuel into the refueling pipe.
In the case where the check valve is provided in the aforesaid manner, normally, the communicating state between the inner portion of the fuel tank and the refueling pipe is cut off by the check valve, and hence the inner portion of the fuel tank is completely sealed when the vent path is clogged. As a result, there may arise such a problem that the increase of the inner pressure of the fuel tank cannot be suppressed due to the evaporation of the fuel in a high temperature state.
In the case of providing the check valve in the aforesaid manner, it is desirable to set the stroke of the valve element at the time of opening and closing the check valve to a sufficiently large value so that the fuel can be smoothly injected into the fuel tank upon the refueling. However, in the case of employing, as a spring for biasing the valve element, a coil spring provided between the valve element and the end wall portion on the fuel end side of the valve casing, if the opening and closing stroke of the valve element is set to the sufficiently large value, the coil spring is liable to fall down. The coil spring can be prevented from falling down if spring guides fitting to the coil spring are projectingly provided at the valve element and the end wall portion of the valve casing, respectively. However, in this case, there arises such a problem that, since both the spring guides interfere with each other, it becomes difficult to set the stroke of the valve element to the sufficiently large value.
Further, the aforesaid related check valve is so arranged that the valve element formed by hard resin is seated on the valve seat portion of the valve casing formed by the hard resin. Thus, in the case where the fuel flows backward from the fuel tank side to the refueling pipe, the valve element collides with the valve seat portion, and thus there is a possibility that the durability and the sealing property of the valve element and the valve seat portion is degraded.
In view of the aforesaid problem of the related art, an object according to a first aspect of the present invention is to provide a check valve for a refueling pipe of a fuel tank with a pressure relief function for suppressing the increase of the pressure within a fuel tank.
In order to attain the aforesaid object, the first aspect of the present invention is arranged in a manner that in a check valve which is provided at the end portion on the fuel tank side of a refueling pipe communicating within the fuel tank so as to prevent the backward flow of the fuel from the fuel tank to the refueling pipe, a bypass hole is formed in the valve element of the check valve so as to communicate the upstream section with the downstream section thereof.
According to such an arrangement, in the case where the pressure within the fuel tank increases, the fuel or vapor within the fuel tank flows toward the refueling pipe side from the fuel tank side through the bypass hole, whereby the increase of the pressure within the fuel tank can be prevented.
In view of the aforesaid problem of the related art, an object according to a second aspect of the present invention is to provide a check valve for a refueling pipe of a fuel tank which can prevent a coil spring from being caused to fall down and can set the stroke of a valve element at the time of opening and closing the check valve to a sufficiently large value.
In order to attain the aforesaid object, the second aspect of the present invention is arranged in a manner that in a check valve which is provided at the end portion on the fuel tank side of a refueling pipe communicating within the fuel tank so as to prevent the backward flow of the fuel from the fuel tank to the refueling pipe, and a coil spring for biasing the valve element of the check valve toward a valve seat portion formed at the refueling pipe side of the valve casing of the check valve is provided between the valve element and the end portion on the fuel tank side of the valve casing, wherein a first spring guide to which outer periphery of one end portion of the coil spring is fitted is provided at one of the valve element and the valve casing, and a second spring guide to which the inner periphery of the other end portion of the coil spring is provided at the other of the valve element and the valve casing.
According to such an arrangement, in the case where the valve element is pushed and opened against the biasing force of the coil spring due to the pressure of the fuel supplied from the refueling pipe, the coil spring is guided by the first and second spring guides, so that the coil spring is prevented from being caused to fall down. Further, since the spring guides are not mutually aligned and therefore do not interfere to each other, the stroke of the valve element can be set to a sufficiently large value.
In view of the aforesaid problem of the related art, an object according to a third aspect of the present invention is to provide a check valve for a refueling pipe of a fuel tank which is excellent in durability and sealing property.
In order to attain the aforesaid object, the third aspect of the present invention is arranged in a manner that in a check valve which is provided at the end portion on the fuel tank side of a refueling pipe communicating within the fuel tank so as to prevent the backward flow of the fuel from the fuel tank to the refueling pipe, and a valve element of the check valve is biased by a biasing spring within the valve casing toward a valve seat portion of a tapered-shape formed at the refueling pipe side of the valve casing of the check valve, wherein a sealing member of elastic material having a lip portion seated on the valve seat portion is attached to the valve element.
According to such an arrangement, since the lip portion of the sealing member is seated on the valve seat portion at the time of the closing operation of the valve element, the impact caused by the collision between the valve seat portion and the valve element can be absorbed or lightened and further respectively the sealing property can be secured due to the elasticity of the lip portion.
Furthermore, in the case where the valve element is formed by a spring receiving member for a biasing spring and a main body member having an outer diameter set to be larger than the minimum diameter of the valve seat portion and smaller than the outer diameter of the lip portion, and further the sealing member is sandwiched between the main body member and the spring receiving member, the sealing member can be firmly held on the valve element. Further, since the main body member abuts against the valve seat portion, excessive bending of the lip portion due to the biasing force of the biasing spring can be prevented, and so the durability of the lip portion is improved and the sealing property thereof is surely secured.